Muon spin relaxation studies of the spin glass AgMn (invited)

Publisher Website
Google Scholar
Abstract
We report measurements of magnetic ion dynamics in the spin-glass sytem AgMn (1.6 at. %) using the muon spin relaxation technique (μSR). The salient features of the theoretical μSR lineshapes in zero and finite longitudinal applied fields are reviewed. Zero-field measurements below the glass temperature (Tg = 7.6 K) exhibit a static width a(T) which decreases with increasing temperature reminiscent of an ’’order parameter’’ behavior. At T≲Tg/2 the static width is consistent with that calculated for a random orientation of frozen Mn spins. The temperature dependence of a(T) is attributed to rapid, small-amplitude fluctuations of the local field about its quasistatic equilibrium position. An apparent stiffening of the fluctuation frequency spectrum is observed as the applied magnetic field is increased. The measured upper limit for frequencies which significantly relax the muon spin is about 50–100 times smaller than the peak in the mode density calculated by Walstedt and Walker in Monte Carlo simulations of small-amplitude harmonic excitations in CuMn (0.9 at. %), a system similar to ours. Above Tg the spin motion changes dramatically, from small-amplitude fluctuations to nearly complete reorientation, as expected. Measurements in longitudinal fields above Tg confirm the anomalous field-induced static broadening reported in earlier transverse field measurements.

This publication has 26 references indexed in Scilit: